The derailment occurred as an evening Paris Austerlitz-Limoges train with 385 passengers on board approached Brétigny-sur-Orge station at 85 mph, below the 93 mph limit for that section of track. The rear part of the train derailed, mounted the platform, and came to rest on parallel tracks.
SNCF says the detached fishplate was discovered in a switch about 650 feet north of the station. Damage to the rear wheelset (see photo, at bottom) of the third coach of the train appears to confirm the hypothesis that the fishplate caused the rear part of the train to derail.
Examination of the locomotive and the derailed coaches did not find any mechanical abnormalities, and the coaches were most recently maintained on June 29. Similarly, no mechanical defects were discovered on the two trains that passed through Brétigny-sur-Orge ahead of the derailed train.
SNCF has launched a national inspection program for approximately 5,000 turnouts to be conducted over the next two weeks. These include double diamond crossings with slip points, single diamond crossings with slips, and diamond crossings.
French President François Hollande has ordered three inquiries into the accident: one by the Ministry of Justice, one by SNCF, and the third by the Ministry of Transport.